Acoustic systems have been used much like optic systems for imaging and analyzing subjects which are optically opaque. It has been suggested that many properties of a subject, such as its geometry, density distribution, and elastic properties of defects, can be analyzed from measurements of acoutic waves scattered from the subject. One problem of such systems is that the scattered acoustic waves include so much information that it is difficult to isolate a parameter of interest. It is further difficult to isolate a particular particle of interest from the surrounding environment.